Evolution's Witness

How Eyes Evolved

Ivan R Schwab

Many insights are new to science and illustrate key steps in the evolution of the eye

Discusses pivotal developments throughout the preceding 3.75 billion years and illustrates how the eye can be practical and utilitarian at each step

Evolution's Witness

How Eyes Evolved

Ivan R Schwab

Description

With predation and carnivory as catalysts, the first known eye appeared in a trilobite during the Cambrian explosion approximately 543 million years ago. This period was a crucible of evolution and teemed with anatomic creativity although the journey to formed vision actually began billions of years before that. The Cambrian period, however, spawned nearly all morphologic forms of the eye, followed by descent over hundreds of millions of years providing an unimaginable variety of eyes with at least ten different designs. Some eyes display spectacular creativity with mirror, scanning or telephoto optics. Some of these ocular designs are merely curiosities, while others offer the finest visual potential packed into a small space, limited only by the laws of
diffraction or physiological optics. For example, some spiders developed tiny, well-formed eyes with scanning optics and three visual pigments; scallops have 40-100 eyes circling their mantle, each of which has mirror optics and contains two separate retinae per eye; deep ocean fish have eyes shaped like tubes containing yellow lenses to break camouflage; and some birds have vision five times better than ours; but this is only part of the story. Each animal alive today has an eye that fits is niche perfectly demonstrating the intimacy of the evolutionary process as no other organ could. The evolution of the eye is one of the best examples of Darwinian principles.Although few eyes fossilize in any significant manner, many details of this evolution are known and understood.
From initial photoreception 3.75 billion years ago to early spatial recognition in the first cupped eyespot in Euglena to fully formed camera style eyes the size of beach balls in ichthyosaurs, animals have processed light to compete and survive in their respective niches.It is evolution's greatest gift and its greatest triumph. This is the story of the evolution of the eye.

2. The age of complex cellular life Proterozoic Early life (2500-543 million years
ago)Inception of EukaryotesNucleated Kleptomaniacs Euglena gracilis ErythropsidiumBridging the Gap to Metozoa Pre-Metazoa Volvox carteri

3. Eukaryotes organize and metozoans ariseNeoproterozoic Cryogenian--850-650 million years agoEdiacaran--650-543 million years ago1000-543 million years agoMulticellular animals Trichoplax adhaerens CoralsDiploastrea helioporaGoniopora species Cubozoan Jellyfish Tripedalia cystophoraCiliary and Rhabdomeric Photoreceptor CellsSensory input The eye and the brain Which came first?The making of an eyePhotoreceptors The Crystalline lens Extraocular Muscles and other
structures(Adnexa)Metazoans and their eyes

4. Early animals prepare the groundEdiacaran Period 650-543 million years ago

13. The age of Tetrapods and TerrestrialsLate Devonian Period 385-362 million years ago, Vertebrate Animalia comes ashoreEL.

Vertebrate quest for land Early tetrapodian eyes LungfishNeoceratodus forsteri Tapetum The challenge of a terrestrial environment FrogsPhyllomedusa bicolor Eyelids and the lacrimal system Extraocular muscles
Tear Glands Cornea and lens Retina and vision Neurologic changes North American Wood Frog Rana sylvatica Consolidation of the assumption of land

14.Terrestrial life flourishesCarboniferous 362-299 million years ago Permian 299-251 million years ago

Evolution's Witness

How Eyes Evolved

Ivan R Schwab

Author Information

Ivan R. Schwab M.D. is currently a professor at the University of California, Davis where he has worked as an Ophthalmologist for over twenty years, and was on the faculty at West Virginia University for seven years before coming to UCD. His strong interest in biology and natural history has led him to investigate a diverse range of topics including ocular stem cells, bioengineered tissues for the eye and comparative optics and physiology. He has published extensively in these fields, with three previous books to his credit, and he was the winner of the 2006 IgNobel for Ornithology. He has combined those interests with one in evolution to produce this text on the evolution of the eye.

Evolution's Witness

How Eyes Evolved

Ivan R Schwab

Reviews and Awards

This book shows what can be achieved by combining insights from sensory physiology with anatomy, phylogeny and the fossil record across the widest range of organisms to document the evolution of a biological system. It demonstrates how the study of living forms can successfully be used to interpret fossil ones, and vice versa. The book's magnificent sweep is all-encompassing, and remarkably up-to-date for such a cross-disciplinary work. It's rare for one person to have such a broad background, but Schwab has achieved this, such that the work provides an example for future studies of the kind.
-Prof. Jennifer A. Clack, ScD, FRS
Professor and Curator of Vertebrate Palaeontology,
University Museum of Zoology

An astounding erudite and exciting visual description of eye evolution, something every inquisitive biologist, veterinarian, neuroscientist, or ophthalmologist should have in their library. This book contains 400 illustrations that define and refine the text providing a unique look at the how the eye was achieved. It is truly one of a kind.
Bruce E. Spivey, M.D., M.S., M.Ed.
President, International Council of Ophthalmology

Schwab's lavishly illustrated book documents the amazing proliferation of eyes across the animal kingdom, in all their variations and all their splendour, and it explains the pathways by which these eyes have evolved. Aimed at the non-specialist but intelligent reader, the book begins with the early evolution of life on earth, and sets the scene for the advent of eyes that took place some 500-600 million years ago (mya). By combining fossil evidence with information from extant "primitive" organisms, Schwab explains current ideas about the simple animals that were present during the Ediacaran period (around 600 mya), about the light-detection mechanisms and the genetic machinery that they possessed, and about the split of these primitive animals into two major divisions
- comprising on the one hand most invertebrates and on the other hand our own line that led to vertebrates and mammals.
(cont'd below)

High on the agenda is the invention, around the time of the Cambrian explosion in body forms (more than 500 mya), and the subsequent re-invention, of the two radically different forms of eye: the camera-style eye (as we have) with a single lens, and the compound eye, with multiple repeated units each having its own lens or mirror. Using beautiful images, Schwab charts the myriad variations on these two themes that have been employed by countless species, extinct and extant, over the course of 500 million years of global experimentation, refinement, and rejection. The result is a stunning book that will serve both to introduce non-specialists to the concepts of evolution and eye evolution and also as a reference work for experts.
Trevor D Lamb
Professor of Neuroscience
John Curtin School of Medical Research
The Australian National University
Canberra, Australia

The evolution of the eye was unquestionably one of the most important innovations in the history of life. Ivan Schwab has synthesized a huge array of disparate information to provide us with an indispensable guide through the complexities of visual systems throughout the animal kingdom.
Richard Fortey FRS FRSL

"Which leads to a just published book -- a most remarkable book -- that needs to be in the library of every school and college, and maybe in every household ...There aren't many books like this one, transformative books that provide a wondrous experience -- especially for young people -- just by turning the pages of mesmerizing illustrations of the evolution of the eyes that are looking at the book... A deep majestic event: human eyes looking at a book explaining the evolution of human eyes. (The only event that I know of with more majesty is the human brain contemplating its own evolution.)" -- Huffington Post

"Evolution's Witness: How the Eyes Evolved is an outstanding book. It can be highly recommended. Every neuroophthalmologist should strongly consider adding this book to their library. It would also be valuable for ophthalmologists, neurologists, and neurosurgeons interested in the field of evolution." -- Walter M. Jay, MD, Neuro-ophthalmology

"Evolution's Witness can serve a variety of uses. For the scholar of vision, it is a comprehensive reference but also a source of inspiration and ideas for new ways to study myriad aspects of vision. For the instructor, it would function well as a textbook in a seminar, since it is laid out in a didactic and accessible way, with clear and engaging writing. With its sumptuous illustration, it would make a great coffee-table book for anyone with an interest in biology. The book is also an implicit riposte to the fallacy that eyes are too complex to have evolved by natural selection, so it will also be useful for those engaged in countering creationist agendas. The book has helpful appendices on detailed anatomical matters that are discussed at many points in the book." --
Daniel Graham, Perception

"This comprehensive and beautifully illustrated text should sit on the shelves of all students, graduates and academics with an interest in evolution, adaptation, neural plasticity and natural history. For those more intimately working in the field of visual neuroscience (including optometrists and ophthalmologists), it provides a unique and holistic perspective that provides the context in which we are all working. The book will also emphasize how inadequate the human visual system is in many ways and how much we can learn from nature. Therefore, I highly recommend you to witness the 'inimitable contrivances' of the eye in evolution and appreciate the exquisite complexity of how different organisms form an optical image of the world and convert this to a neural image
that is recognizable by the central nervous system." -- Clinical and Experimental Optometry

Evolution's Witness

How Eyes Evolved

Ivan R Schwab

From Our Blog

By Ivan R. Schwab
Well, yes, sort of. Dogs see colors, but their span of color vision closely resembles the array of colors seen by 'color blind' males. About 8%, or 1 out of 12 males (humans) and about 1 out of 200 females are 'color blind.' We use that term to describe individuals that are color deficient, but they are not truly color blind.

By Ivan R. Schwab M.D. F.A.C.S.
Sharks always draw a crowd. We have a macabre fascination with these creatures because of their commanding presence and predatory lifestyle. Such a lifestyle demands high quality sensory systems, something sharks have had millions of years to develop.